Avoiding a Mouse-related Musculoskeletal Injury

Repetitive Stress Injury (RSI) is a kind of catch all phrase for many conditions, including:

Carpal Tunnel Syndrome

Tenosynovitis / DeQuervain’s Syndrome

Tendonitis

Thoracic Outlet Syndrome

Trigger Finger

Myofascial Pain Syndrome

Chronic Sprain / Strain

Repetitive Stress Injuries occur from repetitive movements involving a specific set of muscles and joints. Mechanical Onset RSI (MORSI), also known as mouse arm disease (MAD), is a mouse-related musculoskeletal injury that affects millions of people around the world and costs employers and insurers billions of dollars. As we spend increasing amounts of time at our computer workstations, we need to be aware of how the design and arrangement of our equipment can impact our chances of acquiring a mouse-related musculoskeletal injury.

How Do I Avoid a Mouse-Related Musculoskeletal Injury?

The feature photo above is an excellent example of how NOT to use your mouse. The following tips should help you avoid a mouse-related musculoskeletal injury. These same posture principles apply to other input devices (e.g., trackball, touchpad, pen, digitizing puck etc.). Postural variation is a key factor for good ergonomics. Try to regularly vary your posture when you work with a mouse, and in this way you will help to minimize the risk of ergonomic problems. Remember, the best ergonomic mice are designed to allow you to vary your posture while working with the mouse.

Mouse Grip – Hold the mouse gently when moving it over a mousing surface. Cup your hand over the mouse, almost floating, without allowing the mouse to support the weight of your arm. Gripping the mouse tightly will strain the muscles in your arm and hand, which could lead to a mouse-related musculoskeletal injury. Frequent breaks should also be taken and arms stretched to boost circulation and re-oxygenate the hand and finger muscles.

Mouse from the Elbow – The human wrist was not designed for a computer mouse. Operating a mouse is awkward and becomes uncomfortable, because the wrist is turned up to 90 degrees from its most comfortable natural resting position. Any bending of the wrist, either to the side or up and down, can lead to tendon damage or other mouse-related musculoskeletal injury. To help avoid a mouse-related musculoskeletal injury, make controlled mouse movements with the entire lower arm, using your elbow as the pivot point and keep your wrist straight and neutral.

Optimal Mouse Position – The most up-to-date studies show that a slightly reclined sitting posture with the hips flexed at 100 to 115 degrees is ideal if you have to sit at a desk. So, sit back in your chair, relax your arms then lift your mousing hand up, pivoting at the elbow, until your hand is just above elbow level. Your mouse should be positioned somewhere around this point. Don’t use a mouse by stretching to the desk or out to the side of a keyboard. This stresses your back by reducing the angle of your hips and increases your chance of getting a mouse-related musculoskeletal injury.

Protect Your Wrist – Your wrists should never be in direct contact with any surface, including wrist rests and mouse pads. Instead, use the base of your palms to support the weight of your hands and arms in between mousing and typing to keep pressure off the sensitive carpal tunnel area in the wrist. This will help reduce the risk of a mouse-related musculoskeletal injury.

Avoid Restricting Circulation – Blood circulation is responsible for the action that moves nutrients, gases and wastes to and from cells, and helps stabilize body temperature and pH to maintain harmony. When blood vessels constrict, blood does not flow properly. Many people have exposed blood vessels near the skin at the wrist, where the pulse is often taken. Any pressure in this region will disrupt circulation into the hand and this will cause constriction in those blood vessels, which can cause hands and fingertips in the mouse hand to become cold. This can lead to a mouse-related musculoskeletal injury like Carpal Tunnel Syndrome, Arthritis, Raynaud’s, DeQuervain’s, or Tendonitis.

Don’t Use a Wrist Rest – Don’t use wrist rests or splints while typing, experts warn. Research has shown that using a wrist rest doubles the pressure inside the carpal tunnel. According to Professor Alan Hedge, Cornel University, the floor of the tunnel is a more flexible ligament that transmits external pressure changes directly into the carpal tunnel. Are you already suffering from Carpal Tunnel Syndrome (CTS)? One way to find out is by performing a test called “Tinel’s sign”, which simply involves tapping on the palmar surface of the wrist, which is enough to cause tingling and numbness in someone developing CTS.

Avoid Restricting Arm Movement – With a softly padded wrist rest, especially one that is rounded, or a soft chair arm rest the forearm becomes “locked” into position. Mouse movements should be made using the elbow as the pivot point, not the wrist. Too much wrist movement increases intracarpal pressure, leading to a mouse-related musculoskeletal injury.

Mouse Shape – Choose a mouse design that fits your hand, but is as flat as possible to reduce wrist extension. Don’t use a curved mouse. Use a larger, symmetrically shaped mouse, such as the Whale mouse or the Perfit mouse, which encourage arm rather than wrist movements or that encourage postural variety and one or two-handed use. Pen-based mice designs also allow a more comfortable grip. Some types of mouse palm support can be attached to the mouse, such as the Mouse Bean.

Load sharing – If you want to load share between your right and left hands, using the mouse for some of the time with each hand, you need to choose a mouse platform that can easily be configured to the left and/or right and a symmetrical shaped mouse that can be used by either hand.

Other Input Devices

Whether you choose a different mouse design, trackball, joystick, pen, touchpad, multitouch pad, or some other input device, make sure that you position it comfortably and that your wrist stays in a neutral position when using the device to avoid a mouse-related musculoskeletal injury.

How to Position Your Mouse in Your Workspace

Right-handed and left-handed mouse users should position a flat mouse platform, 1-2″ above the keyboard and over the numeric keypad – you can easily move it out of the way if you need to access these keys. With a downward sloping mouse platform, position this close to the side of the keyboard so that you can use the mouse in a neutral wrist position. However, if you are left-handed and have a right-handed keyboard, with the numeric keypad on the right, your best bet would be to use an angle-adjustable mouse platform placed immediately to the left side of the keyboard, and position it so that your left wrist is neutral. Mouse platforms are commercially available. If you require assistance choosing a mouse platform, please call Accredited Rehabilitation Consultants.

Accredited Rehabilitation Consultants not only provides ergonomic evaluations and ergonomic consulting, we also can help you get set up with the ergonomic equipment you need to prevent costly injuries in the workplace. See our Ergonomic Equipment page for more information on how we can help you make appropriate ergonomic selections for your workplace. We have relationships with many manufacturers and will recommend the best options regarding ergonomic equipment on the market.